Department of Psychiatry, Yale University School of Medicine, New Haven, CT06510, USA. nash.boutros@yale.edu

Stimulation parameters seem to strongly influence the efficacy of repetitivetranscranial magnetic stimulation (rTMS) in the management oftreatment-resistant depressed patients. The most effective and safest parametersare yet to be defined. Moreover, systematic follow-up data available to documentthe duration of the therapeutic effects remain sparse. Twenty-onetreatment-resistant depressed patients were randomized to either active rTMS(N=12) or to sham (N=9) treatment in a double-blind design. Patients were kepton their medications. Sub-motor-threshold (MT) stimulation (80% MT) wasdelivered for 10 consecutive work days (20 Hz, 2-s trains, 20 trains). Subjectsmeeting pre-set criteria for responding were entered into a follow-up phase forup to 5 months. Utilizing the above stimulation parameters, we found nosignificant difference between groups. Six patients in the active group and onesubject in the sham group met criteria for the follow-up phase. The period oftime before subjects met criteria for relapse was highly variable ranging from 2to 20 weeks. Sub-threshold rTMS stimulation for 2 weeks is not significantlysuperior to sham treatment for treatment-resistant depressed patients. Theduration of the therapeutic effects of rTMS delivered to the left prefrontalcortex using the above-described parameters is highly variable.